In recent years, a light-emitting element such as an LED has come to be used for general lighting in consideration of the global environment. For example, the non-patent literature 1 below discloses a lighting device in which AC voltage supplied from a commercial power source is converted into DC voltage using a rectifying/smoothing circuit, the DC voltage is applied to an LED array, and the LED array lights up under constant current control. In addition, the patent literature 1 below discloses a lighting device employing a lighting system using an AC current in which AC voltage supplied from a commercial power source is applied to an LED array without conversion.